The list of healthy Boston Celtics players is dwindling by the minute.

Celtics guard Marcus Smart has a torn tendon in his right thumb and is out indefinitely as he seeks a second opinion on the injury, Yahoo Sports’ Shams Charania reported Monday, citing league sources.

Smart’s injury is being called a sprain, according to ESPN’s Adrian Wojnarowski, who reports the team’s medical staff still is unsure if the 24-year-old can play through the injury or will need to miss time.

Smart suffered the injury while diving for a loose ball in Sunday’s loss to the Indiana Pacers and was seen wearing a protective cast on his right hand after the game.

The Pacers game was especially cruel for the Celtics: All-Star guard Kyrie Irving didn’t return for the second half due to a knee injury, while Daniel Theis reportedly tore his meniscus and may miss the rest of the season.

UPDATE (7:25 p.m. ET): Celtics president of basketball operations Danny Ainge provided this update to the Smart story.

UPDATE (3:43 p.m. ET): The C’s acknowledged Smart’s injury Monday afternoon but didn’t provide many further details.

Thumbnail photo via Bob DeChiara/USA TODAY Sports Images